Rhetoric: In the context of Alma’s discourse, sign-seeking is another hindrance to knowledge precisely because it won’t work. Here, however, he is dealing not with the individual case, but the general case of what religion is supposed to be. Alma has a congregation that is willing to hear, and he begins to teach them. This passage is his transition from introduction to the heart of his lesson: the nature of faith. His audience needs this lesson because they have been excluded from ceremonial religion. However, faith will allow them worship regardless of the place and time.
Scripture: Alma creates an important dichotomy between faith and knowledge. They are mutually exclusive. Alma specifically notes that when “a man knoweth a thing he hath no cause to believe.” This is a critical piece of information about faith, which he repeats in verse 21. (See commentary accompanying that verse.)